ORCID Profile
0000-0002-4352-7852
Current Organisation
Nanyang Technological University
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Historical Studies | Asian History | Natural Hazards | Australian History (excl. Aboriginal and Torres Strait Islander History) |
Social Impacts of Climate Change and Variability | Natural Hazards not elsewhere classified | Expanding Knowledge in History and Archaeology
Publisher: Elsevier BV
Date: 2010
Publisher: Copernicus GmbH
Date: 22-05-2017
Publisher: SAGE Publications
Date: 09-2008
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-08-2018
Abstract: Coastal cities safe from tsunami today may become tsunami-prone with sea-level rise.
Publisher: Copernicus GmbH
Date: 09-2010
DOI: 10.5194/NHESS-10-1793-2010
Abstract: Abstract. Comprehensive analysis of 15 previously published regional databases incorporating more than 100 sources leads to a newly revised historical tsunami database for the northeastern (NE) region of the South China Sea (SCS) including Taiwan. The validity of each reported historical tsunami event listed in our database is assessed by comparing and contrasting the information and descriptions provided in the other databases. All earlier databases suffer from errors associated with inaccuracies in translation between different languages, calendars and location names. The new database contains 205 records of "events" reported to have occurred between AD 1076 and 2009. We identify and investigate 58 recorded tsunami events in the region. The validity of each event is based on the consistency and accuracy of the reports along with the relative number of in idual records for that event. Of the 58 events, 23 are regarded as "valid" (confirmed) events, three are "probable" events and six are "possible". Eighteen events are considered "doubtful" and eight events "invalid". The most destructive tsunami of the 23 valid events occurred in 1867 and affected Keelung, northern Taiwan, killing at least 100 people. Inaccuracies in the historical record aside, this new database highlights the occurrence and geographical extent of several large tsunamis in the NE SCS region and allows an elementary statistical analysis of annual recurrence intervals. Based on historical records from 1951–2009 the probability of a tsunami (from any source) affecting the region in any given year is relatively high (33.4%). However, the likelihood of a tsunami that has a wave height m, and/or causes fatalities and damage to infrastructure occurring in the region in any given year is low (1–2%). This work indicates the need for further research using coastal stratigraphy and inundation modeling to help validate some of the historical accounts of tsunamis as well as adequately evaluate the recurrence intervals of tsunamis along the now heavily developed coastlines of the region.
Publisher: Copernicus GmbH
Date: 17-06-2021
DOI: 10.5194/NHESS-21-1887-2021
Abstract: Abstract. Modern tsunami events have highlighted the vulnerability of port structures to these high-impact but infrequent occurrences. However, port planning rarely includes adaptation measures to address tsunami hazards. The 2011 Tohoku tsunami presented us with an opportunity to characterise the vulnerability of port industries to tsunami impacts. Here, we provide a spatial assessment and photographic interpretation of freely available data sources. Approximately 5000 port structures were assessed for damage and stored in a database. Using the newly developed damage database, tsunami damage is quantified statistically for the first time, through the development of damage fragility functions for eight common port industries. In contrast to tsunami damage fragility functions produced for buildings from an existing damage database, our fragility functions showed higher prediction accuracies (up to 75 % accuracy). Pre-tsunami earthquake damage was also assessed in this study and was found to influence overall damage assessment. The damage database and fragility functions for port industries can inform structural improvements and mitigation plans for ports against future events.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-21113
Abstract: & & When modelling tsunamis and assessing tsunami hazard, it is frequently necessary to make simplifying assumptions in order to reduce the problem to one which is computationally tractable within a reasonable period of time. In this paper, we examine the key factors controlling the generation of the initial sea surface wave and present a series of clear and simple guidelines for real-world problems. We also provide number of computational resources (a tsunami loader) which may be utilised with existing tsunami propagation codes (e.g. COMCOT) to modify the initial sea-surface way, where necessary.& & & & & & & & & Most tsunami modelling codes operate under the assumption that the initial sea surface wave is identical to the seafloor perturbation. Yet this is only true for large tsunami sources (Kajiura 1963). With our tsunami loader we model the tsunamigensis process and the formation of the initial sea-surface wave. Critically, the diffusive effect of the water column above the deforming seafloor is accurately addressed, which can result in a substantial decrease in the energy in the initial sea-surface wave.& & & & & & & & & For ex le, let us consider a rectangular uplifting patch on the seafloor, at a depth of 4km. For a 4x4km square patch, the diffusive effect will result in an energy reduction of 90%. Even if one of those dimensions is 100 times larger, such that we have a relatively large 400x4 km uplifting region, the energy reduction is still 70%. We find the shortest dimension of the uplifting patch provides a strong control on the energy of the initial sea-surface wave, and consequential tsunami. If we move to a 40x40 km square patch we find the reduction is now 20%, and 400x40 km patch is now a relatively modest, but non-negligible 12%.& & & & & & & & & We also include other effects such as the time-dependence of seafloor deformation, which also reduces the potential tsunami energy, and horizontal advection of topography, which conversely increases the potential tsunami energy, in our analysis of the tsunamigenesis process. Currently implemented for fault sources, we are working to include landslide and volcanic sources.& &
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-189
Abstract: The 2004 Indian Ocean, 2010 Chile and 2011 Tohoku-Oki tsunami events have demonstrated the destructiveness of tsunami to both near and far-field communities. Globally, many coastal cities have started to place more emphasis on preparing for these rare but potentially catastrophic events by developing probabilistic tsunami hazard assessments (PTHAs). Previous work in the region has identified the Manila Trench to be a potential tsunami source within the South China Sea. Here we model the wave propagations from heterogeneous fault slips, for magnitudes ranging from 7.4 to 8.4, along the southern segment of the Manila Trench, and develop hazard curves for 52 sites in equatorial Southeast Asia. Our results show that the hazard, based on wave heights and arrival times, is variable on both the regional and local scales. Amongst the Southeast Asian countries studied, the Philippines and Vietnam are identified to be most at risk, with high mean peak nearshore litudes and short wave travel times. The least impacted countries include Singapore, western Malaysia, Indonesia (excluding the Natuna Islands), Thailand and Cambodia. Although the hazard for Singapore appears to be low, tides and wave run-up are not accounted for in this regional study. To address this we re-model the worst-case scenario adjusting for the highest astronomical tides and bottom friction. Our preliminary results show that Singapore can experience maximum wave heights up to 0.15 m. The relatively low wave heights yield low maximum inundation distances and suggest that the tsunamigenic hazard in Singapore is low. Hazard from tsunami currents, however, remains undetermined at this stage.
Publisher: Elsevier BV
Date: 10-2012
Publisher: Research Square Platform LLC
Date: 18-09-2023
Publisher: Research Square Platform LLC
Date: 26-05-2023
DOI: 10.21203/RS.3.RS-2950249/V1
Abstract: Submarine volcanism represents approximately 85% of volcanism taking place on Earth, and submarine eruptions can be particularly hazardous due to their potential to cause large-scale hazards from sector collapses, tsunamis, and ash dispersal. While recent eruptions in the Kingdom of Tonga and Japan have highlighted the significant hazards posed by submarine volcanoes, there has been little to no study of submarine volcanoes in Southeast Asia and its surroundings. Here we present and provide the SEATANI dataset, which compiles a list of 466 seamounts from the region, from different published sources. We characterized them in GIS, based on their shape and inferred evolution stage, which helped us to infer their past hazard history, and identified areas where the hazard posed by submarine volcanic eruptions is likely to be higher, based on exposure analyses. Our results show that there is a large number of potentially hazardous seamounts in this region, and Taiwan had the highest hazard and the highest exposure. Philippines, Indonesia and Vietnam were also found to have relatively high exposure. The results from this work serve as a first step for southeast Asian and neighbouring countries to become more resilient against and prepared for submarine volcanic eruptions in the region.
Publisher: Springer Science and Business Media LLC
Date: 08-10-2021
Publisher: Copernicus GmbH
Date: 12-05-2021
DOI: 10.5194/NHESS-21-1473-2021
Abstract: Abstract. Vietnam is a major rice producer, and much of the rice grown is concentrated in the Red River Delta (RRD) and the Mekong River Delta (MRD). While the two deltas are highly productive regions, they are vulnerable to natural hazards and the effects of human-induced environmental change. To show that the processes and issues affecting food security are reinforcing, interdependent and operating at multiple scales, we used a systems-thinking approach to represent the major linkages between anthropogenic land-use and natural hazards and elaborate on how the drivers and environmental processes interact and influence rice growing area, rice yield and rice quality in the two deltas. On a local scale, demand for aquaculture and alternative crops, urban expansion, dike development, sand mining and groundwater extraction decrease rice production in the two deltas. Regionally, upstream dam construction impacts rice production in the two deltas despite being distally situated. Separately, the localized natural hazards that have adversely affected rice production include droughts, floods and typhoons. Outbreaks of pests and diseases are also common. Climate-change-induced sea level rise is a global phenomenon that will affect agricultural productivity. Notably, anthropogenic developments meant to improve agricultural productivity or increase economic growth can create many unwanted environmental consequences such as an increase in flooding, saltwater intrusion and land subsidence, which in turn decreases rice production and quality. In addition, natural hazards may lify the problems created by human activities. Our meta-analysis highlights the ways in which a systems-thinking approach can yield more nuanced perspectives to tackle “wicked” and interrelated environmental challenges. Given that deltas worldwide are globally significant for food production and are highly stressed and degraded, a systems-thinking approach can be applied to provide a holistic and contextualized overview of the threats faced in each location.
Publisher: Copernicus GmbH
Date: 29-11-2018
DOI: 10.5194/NHESS-18-3167-2018
Abstract: Abstract. On 23 August 2017 a Category 3 hurricane, Typhoon Hato, struck southern China. Among the hardest hit cities, Macau experienced the worst flooding since 1925. In this paper, we present a high-resolution survey map recording inundation depths and distances at 278 sites in Macau. We show that one-half of the Macau Peninsula was inundated, with the extent largely confined by the hilly topography. The Inner Harbor area suffered the most, with a maximum inundation depth of 3.1 m at the coast. Using a combination of numerical models, we simulate and reproduce this typhoon and storm surge event. We further investigate the effects of tidal level and sea level rise on coastal inundations in Macau during the landfall of a “Hato-like” event.
Publisher: Springer Science and Business Media LLC
Date: 07-09-2013
Publisher: Springer Science and Business Media LLC
Date: 10-02-2017
DOI: 10.1038/NCOMMS14387
Abstract: Sea-level rise is a global problem, yet to forecast future changes, we must understand how and why relative sea level (RSL) varied in the past, on local to global scales. In East and Southeast Asia, details of Holocene RSL are poorly understood. Here we present two independent high-resolution RSL proxy records from Belitung Island on the Sunda Shelf. These records capture spatial variations in glacial isostatic adjustment and paleotidal range, yet both reveal a RSL history between 6850 and 6500 cal years BP that includes two 0.6 m fluctuations, with rates of RSL change reaching 13±4 mm per year (2 σ ). Observations along the south coast of China, although of a lower resolution, reveal fluctuations similar in litude and timing to those on the Sunda Shelf. The consistency of the Southeast Asian records, from sites 2,600 km apart, suggests that the records reflect regional changes in RSL that are unprecedented in modern times.
Publisher: Copernicus GmbH
Date: 31-07-2019
DOI: 10.5194/NHESS-19-1565-2019
Abstract: Abstract. Seismogenic tsunami hazard assessments are highly dependent on the reliability of earthquake source models. Here in a study of the Manila subduction zone (MSZ) system, we combine the geological characteristics of the subducting plate, geometry, and coupling state of the subduction interface to propose a series of fault rupture scenarios. We ide the subduction zone into three rupture segments: 14–16, 16–19, and 19–21.7∘ N inferred from geological structures associated with the down-going Sunda plate. Each of these segments is capable of generating earthquakes of a magnitude between Mw=8.5+ and Mw=9+, assuming a 1000-year seismic return period as suggested by previous studies. The most poorly constrained segment of the MSZ lies between 19 and 21.7∘ N, and here we use both local geological structures and characteristics of other subduction zone earthquakes around the world, to investigate the potential rupture characteristics of this segment. We consider multiple rupture modes for tsunamigenic earthquake and megathrust-splay fault earthquakes. These rupture models facilitate an improved understanding of the potential tsunami hazard in the South China Sea (SCS). Hydrodynamic simulations demonstrate that coastlines surrounding the SCS could be devastated by tsunami waves up to 10 m if large megathrust earthquakes occur in these segments. The regions most prone to these hazards include west Luzon of Philippines, southern Taiwan, southeastern China, central Vietnam, and Palawan Island.
Publisher: American Geophysical Union (AGU)
Date: 30-07-2023
DOI: 10.1029/2023JF007125
Abstract: Understanding the temporal‐spatial patterns of modern and relict sediments is of importance for assessing changes in the Quaternary environment and sea‐level. Sedimentological and geochemical data is presented, along with in situ shell‐based accelerator mass spectrometry 14 C ages of 30 s les from the surface sediments on the northern shelf of the South China Sea (NSSCS). The authors’ data show that the NSSCS surface sediments exhibit considerable ersity in composition. Modern sediments are primarily constrained to the NW inner shelf, which is fed by fluvial sands sourced from Coastal South China river systems and dominated by the Pearl River Estuary delivery. The transport and discharge of the terrestrial sediments to the NSSCS is highly influenced by the Guangdong Longshore Current and its secondary cyclonic eddies. Relict sediments dominated by well‐sorted, medium‐ and coarse‐grained sands were identified in the NW Shenhu and NW Dongsha areas of the outer NSSCS. The sedimentology and geochemistry of the relict sediments imply that they were deposited in a dry and cold environment either during the low sea levels of the late Pleistocene (∼40 ka) or the early Holocene (∼10 ka). To the east, the Taiwan Shoal and vicinity are dominated by a sand mixture, at which the relict sediments were reworked by terrigenous supply and modern hydrodynamic environment due to the compound action of the Guangdong Longshore Current, seasonal cyclones, and Kuroshio Intrusion. The present isobaths of ∼−90 m in the NSSCS might be the reflective of the early Holocene coastal delta or the last glacial maximum shoreline.
Publisher: Copernicus GmbH
Date: 20-11-2021
Abstract: Abstract. The tsunami hazard posed by the Flores backarc thrust, which runs along the northern coast of the islands of Bali and Lombok, Indonesia, is poorly studied compared to the Sunda megathrust, situated ~250 km to the south of the islands. However, the 2018 Lombok earthquake sequence demonstrated the seismic potential of the western Flores Thrust when a fault r beneath the island of Lombok ruptured in two Mw 6.9 earthquakes. Although the uplift in these events mostly occurred below land, the sequence still generated 1–2.5 m-high local tsunamis along the northern coast of Lombok (Wibowo et al., 2021). Historical records show that the Flores fault system in the Lombok and Bali region has generated at least six ≥ Ms 6.5 tsunamigenic earthquakes since 1800 CE. Hence, it is important to assess the possible tsunami hazard represented by this fault system. Here, we focus on the submarine fault segment located between the islands of Lombok and Bali (below the Lombok Strait). We assess modeled tsunami patterns generated by fault slip in six earthquake scenarios (slip of 1–5 m, representing Mw 7.2–7.9+), with a focus on impacts on the capital cities of Mataram, Lombok and Denpasar, Bali, which lie on the coasts facing the strait. We use a geologically constrained earthquake model informed by the Lombok earthquake sequence (Lythgoe et al., 2021), together with a high-resolution bathymetry dataset developed by combining direct measurements from GEBCO with sounding measurements from the official nautical charts for Indonesia. Our results show that fault rupture in this region could trigger a tsunami reaching Mataram in 8 minutes and Denpasar in ~10–15 minutes, with multiple waves. For an earthquake with 3–5 m of coseismic slip, Mataram and Denpasar experience maximum wave heights of ~1.3–3.3 m and ~0.7 to 1.5 m, respectively. Furthermore, our earthquake models indicate that both cities would experience coseismic subsidence of 20–40 cm, exacerbating their exposure to both the tsunami and other coastal hazards. Overall, Mataram city is more exposed than Denpasar to high tsunami waves arriving quickly from the fault source. To understand how a tsunami would affect Mataram, we model the associated inundation using the 5 m slip model and show that Mataram is inundated ~55–140 m inland along the northern coast and ~230 m along the southern coast, with maximum flow depths of ~2–3 m. Our study highlights that the early tsunami arrival in Mataram, Lombok gives little time for residents to evacuate. Raising their awareness about the potential for locally generated tsunamis and the need for evacuation plans is important to help them respond immediately after experiencing strong ground shaking.
Publisher: Research Square Platform LLC
Date: 18-11-2022
DOI: 10.21203/RS.3.RS-2157980/V1
Abstract: Low-lying equatorial islands are susceptible to relative sea level (RSL) rise. Here, we quantify magnitudes and rates of RSL change since the last glacial maximum (LGM) to provide probability perspectives of future sea level. Geological reconstructions and instrumental records from the Sunda Shelf and Singapore show RSL rose ~ 121 m at rates up to ~ 15 mm/yr since the LGM, which reduced the paleogeographic landscape by ~ 2.3 million km 2 . In the 20th century, RSL began to rise, increasing at a rate of ~ 1.7 mm/yr to ~ 2.2 mm/yr between 1915 and 2020 CE. Future projections under a moderate emissions scenario show RSL rising 0.95 m at a rate of 7.3 mm/yr by 2150 which has only been exceeded (at least 99% probability) during rapid ice melting events ~ 14.5 and ~ 9 thousand years ago. Future projections under a high emissions scenario incorporating low confidence ice-sheet processes, however, have no precedent since the LGM.
Publisher: Geological Society of London
Date: 2012
DOI: 10.1144/SP361.6
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-22090
Abstract: & & & & & & & & strong& Can we distinguish tsunami and storm deposits based on their microbial composition?& /strong& & & & & & & & & & Wenshu Yap& sup& ,2,3& /sup& , Adam D. Switzer & sup& ,2& /sup& , Chris Gouramanis& sup& & /sup& , Dale Dominey-Howes& sup& & /sup& , Maurizio Labbate& sup& & /sup& , Federico M. Lauro& sup& ,3& /sup& & & & & & & & & & & sup& & /sup& Asian School of the Environment, Nanyang Technological University, 50 Nanyang Drive, Singapore 639798& & & & & sup& & /sup& Earth Observatory of Singapore, Nanyang Technological University, 50 Nanyang Drive, Singapore 639798& & & & & sup& & /sup& Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, 60 Nanyang Drive, Singapore 639798& & & & & sup& & /sup& Department of Geography, National University of Singapore, Kent Ridge, Singapore 117570& & & & & sup& & /sup& Asia-Pacific Natural Hazards and Disaster Risk Research Group, School of Geosciences, University of Sydney, NSW 2006, Australia& & & & & sup& & /sup& School of Life Sciences, University of Technology Sydney, NSW 2007, Australia& & & & & & & & & One of the challenges in the study of coastal hazard is to reliably distinguish between storm and tsunami deposited sediments. This limitation compromises the quality and accuracy of reconstructing historical coastal flooding records, and is thus an issue to a variety of policy makers and stakeholders interested in assessing the risk and vulnerability of coastal communities. Here we describe a microbial community signature based on licon sequencing of DNA extracted from environmental s les collected from two different locations i.e. Cuddalore, India and Phra Thong Island, Thailand. Both locations were impacted by the 2004 Indian Ocean Tsunami and a subsequent storm event. Our results show that the microbial community in the tsunami deposits are significantly different from that found in the storm deposits as well as soil and terrestrial sediments (PERMANOVA, p-value & .01) in both locations. The microbial community differences between the tsunami deposits and storm deposits are not statistically correlated with chemical data such as total Nitrogen, total Carbon and total Sulfur, implying that our microbial signature is insensitive to environmental and geochemical variability. Integrating molecular techniques to investigate geological records is powerful and statistically robust in discriminating between modern tsunami and storm deposits.& &
Publisher: Coastal Education and Research Foundation
Date: 07-2005
DOI: 10.2112/04-0177.1
Publisher: Springer Science and Business Media LLC
Date: 18-06-2021
DOI: 10.1038/S43247-021-00199-3
Abstract: Sandy onshore deposits from tsunamis are difficult to distinguish from storm deposits, which makes it difficult to assess coastal hazards from the geological record. Here we analyse environmental DNA from microbial communities preserved in known tsunami and storm-deposited sediments and intercalating soils and non-marine sediments near Cuddalore, India, and Phra Thong Island, Thailand. Both sites were impacted by the 2004 Indian Ocean Tsunami and a subsequent storm flooding event (2011 Cyclone Thane at Cuddalore and a 2007 storm at Phra Thong Island). We show that the microbial communities in the overwash deposits are significantly different from soil and sediments that are not derived by overwash processes at both locations. Our method also successfully discriminates between modern tsunami deposits and storm deposits. We suggest molecular techniques have the potential to accurately discriminate overwash deposits from catastrophic natural events.
Publisher: Copernicus GmbH
Date: 28-10-2020
Publisher: Copernicus GmbH
Date: 27-08-2018
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.MARPOLBUL.2011.02.011
Abstract: A 182-year long record of trace metal concentrations of aluminum, zinc and lead was reconstructed from a massive Porites coral skeleton from southeastern Hong Kong to evaluate the impacts of anthropogenic activity on the marine environment. Zn/Ca and Pb/Ca ratios fluctuate synchronously from the early 19th century to the present, indicating that the marine environment has been anthropogenically influenced since industrialization. Additionally, land reclamation, mining, and ship building activities are recorded by elevated Al/Ca ratios from 1900 to 1950. The coral record indicates that high levels of Zn, Pb and Al occur coincidentally with local wars, and may have contributed to partial colony mortality. Pb/Ca does not correlate well with hemispheric proxy records after 1950, indicating that coastal corals may be recording local rather than hemispheric contamination. Pb/Ca levels in Hong Kong, Guangdong and Hainan corals imply a continuous supply of Pb-based contamination to southern China not reflected in hemispheric signals.
Publisher: Elsevier BV
Date: 2006
Publisher: Elsevier BV
Date: 07-2010
Publisher: Copernicus GmbH
Date: 20-06-2022
DOI: 10.5194/ICG2022-348
Abstract: & & The Shark Bay Marine Park in Australia is a UNESCO World Heritage Property in a region of marginal tropical cyclone influence and its sustainability requires a deep consideration of cyclone hazards. Here, we analyse historical records of a large storm surge from a Tropical Cyclone in 1921 that generated remarkable overland flow leaving fish and sharks stranded over 9 km inland. We weight information from the historical archives in a new framework and model event scenarios to reconstruct its magnitude. The plausible event scenarios imply that the cyclone was a marginal Category 4 or 5 storm with a return interval equivalent or slightly greater than the regional planning level. The outcome underscores the importance of examining the pre-instrumental events in areas of marginal cyclone influence as they are commonly of key economic importance.& Our work also implies that TC risk affects marine conservation in the Shark Bay World Heritage Property and requires attention.& &
Publisher: Copernicus GmbH
Date: 28-10-2020
Abstract: Abstract. Modern tsunami events have highlighted the vulnerability of port structures to these high-impact but infrequent occurrences. However, port planning rarely includes adaptation measures to address tsunami hazards. The 2011 Tohoku tsunami presented us with an opportunity to characterise the vulnerability of port industries to tsunami impacts. Here, we provide a spatial assessment and photographic interpretation of freely available data sources. Approximately 5,000 port structures were assessed for damage and stored in a database. Using the newly developed damage database, tsunami damage is quantified statistically for the first time, through the development of damage fragility functions for eight common port industries. In contrast to tsunami damage fragility functions produced for buildings from existing damage database, our fragility functions showed higher prediction accuracies (up to 75 % accuracy). Pre-tsunami earthquake damage was also assessed in this study, and was found to influence overall damage assessment. The damage database and fragility functions for port industries can inform structural improvements and mitigation plans for ports against future events.
Publisher: Copernicus GmbH
Date: 13-07-2020
Abstract: Abstract. Vietnam is a major rice producer and much of the rice grown is concentrated in the Red River Delta (RRD) and the Mekong River Delta (MRD). While the two mega-deltas are highly productive regions, they are vulnerable to natural hazards and the effects of human related environmental change. The natural hazards that affect Vietnam include typhoons, floods and droughts while the major anthropogenic developments happening in Vietnam include dike development, sand mining, dam construction and groundwater extraction. Outbreaks of pests and diseases are also common. Although there is a substantial volume of work investigating the environmental impacts of these natural hazards and anthropogenic interventions, few studies have examined the implications of these on food security. To show that the processes and issues affecting food security are reinforcing and interdependent, we used a systems thinking approach to represent the ways in which natural hazards, anthropogenic land-use and climate change affect rice production in the two mega-deltas. A key finding is that anthropogenic developments meant to improve agricultural productivity or increase economic development create many unwanted environmental consequences such as an increase in flooding, saltwater intrusion and land subsidence which in turn create other negative feedbacks on rice production and quality. In addition, natural hazards may lify the problems created by human activities. In future, besides creating new environmental threats, climate change may exacerbate the effects of natural hazards by increasing the frequency and severity of natural disasters. Our meta-analysis highlights the ways in which a systems thinking approach can yield more nuanced perspectives to tackle complex and interrelated environmental challenges. Given that mega-deltas worldwide are globally significant for food production and are highly stressed and degraded landscapes, a systems thinking approach can be applied to provide a holistic and contextualized overview of the threats faced in each location.
Publisher: SAGE Publications
Date: 08-2008
Abstract: A distinct lens of marine sand, up to 90 cm thick, confined vertically by peat, is found in the upper fill of a closed freshwater back-barrier lagoon on the southeast Australian coast. Coring of the deposit suggests it extends continuously up to 600 m inland and tapers landward rising to ~1.6 m above principle datum. In places the sand is overlain by accumulations of organic-rich silt that contain charophytes, indicating re-establishment of lagoon conditions. Hypotheses considered for the deposition of the sandsheet are higher Holocene sea level, storms and tsunami. Ground-penetrating radar transects of the seaward dune system suggest a penecontemporaneous erosional contact between a series of truncated pre-event dunes and several small overlying post-event dunes. Dating the sandsheet was problematic but it is confined to the last 800 years. The young age combined with a lack of associated beach deposits and evidence of wave scouring suggest that a higher sea-level hypothesis is unlikely. This sand lens is attributed to a large-scale washover event from the southeast. Based on comparisons with modern storm deposits from the same coast and sedimentological diagnostic criteria derived from studies of modern storm- and tsunami-deposited sandsheets, it is concluded that this sand deposit is the product of a short-lived, large-scale overwash event attributed to a late-Holocene tsunami.
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-1935
Abstract: & & Investigating palaeotsunami deposits is a primary way to extend the tsunami database beyond relatively short instrumental and historical records. Such information is essential to reconstruct the frequency and magnitude of past coastal flooding events, which are a key to assess the impact and risk of tsunami to the coastal community. However, palaeotsunami studies are limited as most of the proxies, such as microfossil and geochemical signals, can be modified or degraded with time. Here, we present the application of DNA analysis to investigate a series of palaeotsunami deposits up to ~2800-years-old from a coastal beach ridge sequence on Phra Thong Island (Thailand). Our result shows that it is possible to accurately discriminate palaeotsunami deposits from intercalating organic mud layers using the microbial communities recovered from DNA preserved in the sediment of the geological record. Our work demonstrates that environmental DNA represents a new and promising tool for investigating historical and pre-historical tsunami records.& &
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-2435
Abstract: & & & strong& Shark Bay Marine Park is a UNESCO World Heritage Property in a region of marginal tropical cyclone influence and its sustainability requires a deep consideration of cyclone hazards. Here, we analyse historical records of a large storm surge from a Tropical Cyclone in 1921 that generated remarkable overland flow leaving fish and sharks stranded over 9 km inland. We weight information from the historical archives in a new framework and model event scenarios to reconstruct its magnitude. The plausible event scenarios imply that the cyclone was a marginal Category 4 or 5 storm with a return interval equivalent or slightly greater than the regional planning level. The outcome underscores the importance of examining the pre-instrumental events in areas of marginal cyclone influence as they are commonly of key economic importance.& Our work also implies that TC risk affects marine conservation in the Shark Bay World Heritage Property and requires attention. & /strong& & &
Publisher: Copernicus GmbH
Date: 14-03-2022
DOI: 10.5194/NHESS-2022-4
Abstract: Abstract. Information on agriculture-related damage and losses in Asia is under-reported in major multi-peril disaster databases. National disaster databases in some countries may have information on agricultural losses, but this information is not always available. We address this knowledge gap by creating a database of cyclone-induced rice damage from 1970–2018 for four major rice producing countries in Asia which experience frequent and intense tropical cyclones as a result of their geographical location (Philippines, Vietnam, Bangladesh, and Myanmar). We collated information using online news sources on rice damage locations, rice area damaged, loss in rice production, and loss in rice value from 1970–2018. Of the 1,046 cyclone events recorded, 138 events were associated with rice damage and loss, and majority of these events (93 %) happened in the Philippines and Vietnam. The average area of rice damaged per cyclone event ranged from 42,407 ha in Vietnam to 423,075 ha in Myanmar. The average rice production loss per cyclone event ranged from 460,667 metric tonnes in Bangladesh to 2,943,088 metric tonnes in the Philippines. Losses in rice production value from 1970–2018 were only reported in the Philippines and amounted to an average of US$42 million per cyclone event. Although Category 4 events tend to cause the most damage, tropical storms and Category 1 events were more frequent, especially in Vietnam. While our study is limited by the availability and quality of online news sources, we provide an assessment of rice agricultural damage from tropical cyclones in major rice producing countries in Asia.
Publisher: Copernicus GmbH
Date: 27-08-2018
Abstract: Abstract. On August 23, 2017 a Category 3 Typhoon Hato struck Southern China. Among the hardest hit cities, Macau experienced the worst flooding since 1925. In this paper, we present a high-resolution survey map recording inundation depths and distances at 278 sites in Macau. We show that one half of the Macau Peninsula was inundated with the extent largely confined by the hilly topography. The Inner Harbor area suffered the most with the maximum inundation depth of 3.1 m at the coast. Using a combination of numerical models, we simulate and reproduce this typhoon and storm surge event. We further investigate the effects of tidal level and sea level rise on coastal inundations in Macau during the landfall of a Hato like event.
Publisher: Copernicus GmbH
Date: 28-01-2022
DOI: 10.5194/NHESS-22-213-2022
Abstract: Abstract. Tropical cyclones have devastating impacts on the environment, economies, and societies and may intensify in the coming decades due to climate change. Stable water isotopes serve as tracers of the hydrological cycle, as isotope fractionation processes leave distinct precipitation isotopic signatures. Here we present a record of daily precipitation isotope measurements from March 2014 to October 2015 for Metropolitan Manila, a first-of-a-kind dataset for the Philippines and Southeast Asia. We show that precipitation isotopic variation at our study site is closely related to tropical cyclones. The most negative shift in δ18O values (−13.84 ‰) leading to a clear isotopic signal was caused by Typhoon Rammasun, which directly hit Metropolitan Manila. The average δ18O value of precipitation associated with tropical cyclones is −10.24 ‰, whereas the mean isotopic value for rainfall associated with non-cyclone events is −5.29 ‰. Further, the closer the storm track is to the s ling site, the more negative the isotopic values are, indicating that in situ isotope measurements can provide a direct linkage between isotopes and typhoon activities in the Philippines.
Publisher: Copernicus GmbH
Date: 13-07-2020
Publisher: SAGE Publications
Date: 12-10-2012
Abstract: Understanding the mid-Holocene dynamics of the East Asian monsoon (EAM) is integral to improving models of the Holocene development of the global climate system. Here we reconstruct the mid-Holocene EAM history from the Pearl River estuary, southern China, using bulk organic carbon isotopes (δ 13 C), total carbon to total nitrogen (C/N) ratios and total organic carbon (TOC) concentration. Sedimentary δ 13 C, C/N and TOC are potentially good indicators of changes in monsoonal precipitation strength. Sediments buried during a period of high precipitation exhibit a high proportion of terrigenous material, and have low δ 13 C and high C/N, and vice versa during a period of low precipitation. Results suggest a general decreasing trend in monsoonal precipitation from 6650 to 2150 cal. yr BP because of the weakening Northern Hemisphere insolation most likely related to the current precession circle. Superimposed on this trend are apparent dry–wet oscillations at centennial to millennial timescales most likely in response to solar activity. Mismatches between our δ 13 C record and results from the Dongge Cave in southern China at millennial timescales may indicate that the δ 13 C from the Pearl River estuary reveals changes in precipitation over a broader area than the δ 18 O from Dongge Cave.
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-12629
Abstract: & & Our team has previously built a ~7500 year tsunami history for the northern patch of the Sunda Megathrust. However, the paleo-tsunami history south of Aceh province and the 2004 rupture patch remains poorly understood. We conducted geological investigation to better define the boundaries of rupture patches along the Megathrust.& & & & & & & & & We utilized satellite imagery to pinpoint potential sites likely to archive evidence of paleo tsunami inundations and co-seismic land-level change. Due to the continuing Covid-19 pandemic and restrictions, our researchers from Singapore, and USA could not travel to Indonesia. However, because of the longstanding close collaboration between the Earth Observatory of Singapore and Syiah Kuala University, Banda Aceh, Indonesia, the project continued to progress. The Syiah Kuala University team investigated nearly 20 sites between Banda Aceh in the northern patch of the of Sumatra Megathrust and Padang in the south. Several sites preserved probable paleo-tsunami sediments. The paleo-tsunami sediments were identified from anomalous layers of sand in low energy environments where they would not normally occur, such as mangroves, coastal lowlands, and/or swales.& & & & & & br& Here we present results of litho-, bio- and chronostratigraphical analysis from Susoh as well as preliminary information from sites along the coastline between Meulaboh and Padang. From Susoh we described stratigraphy from a series of cores to a depth of 4.75 m. The top 2.5 meters was dominated by muds typical of estuarine or tidal flat settings, but it is interrupted by three pulses of sandy muds. At 2.55 m we encountered a 0.2 m thick layer of course sand, underlain by a 0.5 m thick mangrove peat with a gradual transition into organic sandy muds and sands. Pollen analysis from the fine-grained organic layers indicate they were formed in a mangrove environment. Radiocarbon dating of the organic macrofossils from the mangrove peat indicate the tsunami event occurred post 1850 cal. yrs BP. Our research continues to improve our understanding of the Sumatran Megathrust.& &
Publisher: Elsevier BV
Date: 06-2013
Publisher: Elsevier BV
Date: 08-2013
Publisher: Copernicus GmbH
Date: 02-01-2020
Publisher: American Geophysical Union (AGU)
Date: 07-12-2017
DOI: 10.1002/2017GL075504
Publisher: SAGE Publications
Date: 2009
Abstract: This paper reconstructs the evolutionary history of the Pearl River delta over the last 9000 years and investigates land—sea interaction in a large deltaic complex which formed under the influence of Asian monsoon climate. Specifically, this research examines the delta evolution in the context of three driving mechanisms: (1) rising sea level that influences the available accommodation space, (2) fluvial discharge as influenced by monsoon climate and (3) human activities that alter sedimentation within the deltaic system. Results reveal that the formation of deltaic sequences was initiated as a consequence of rapid sea-level rise between 9000 and 7000 cal. yr BP. The rate of sea-level rise slowed down markedly around 7000 cal. yr BP and sedimentation switched from transgressive to regressive. Initially, both the progradation of the delta plains near the apex and aggradation of delta front sedimentation in the central and lower parts of the receiving basin were fast owing to strong monsoonal-driven runoff. The progradation rate gradually slowed down between 6800 and 2000 cal. yr BP as monsoonal-driven runoff weakened. Rapid shoreline advances during the last 2000 years were the result of significantly increased human activities, a practice that trapped sediments in the encircled tidal flats along the front of delta plains. The evolutionary history of the Pearl River delta demonstrates the interplay between the three driving mechanisms.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-6822
Abstract: & & On 28 September 2018, a magnitude 7.5 earthquake struck north of Palu, Central Sulawesi, Indonesia. The earthquake generated a tsunami with inundation depths of up to 7.5 m and run-up of up to 10 m above sea level. Inundation distances were only partly topography dependent and reached less than 400 m inland even where terrain did not rise steeply beyond that point. A subsequent tsunami was generated by a combination of minor fault displacement and multiple submarine landslides. In places, co-seismic coastal subsidence of & m exacerbated the tsunami inundation. During a post-event field survey in November 2018, we s led three transects for sediment analysis two in Palu City and one on the eastern coast of Palu Bay. The tsunami deposits in Palu City are predominantly massive, fine- to medium-grained sand in thin layers (& cm) with patchy distribution of sediments. In contrast, sediments present near Pantoloan on the east coast of Palu Bay were coarser (medium- to coarse-grained sand), thicker (up to 12 cm) and more continuous. These tsunami deposits exhibited fining and thinning landwards, and are characterized by a continuous sand sheet that extends up to 250 m inland with few post depositional changes. The grain size ranges from coarse-grained sand to silty-fine-grained sand at the landward extent. The Pantoloan site also contained wave-transported blocks of sea wall weighing up to 4.7 t in addition to sandy deposits. The blocks together with grain size data suggest that water velocities reached 3 m.s& sup& -1& /sup& at more than 130 m from the coast. The tsunami deposits of Palu Bay generally exhibit sedimentological and stratigraphic characteristics shared by storm and tsunami deposits, which maybe be ascribed to the short wave length, relatively low power and short-term inundation of the tsunami and the limited availability of sediments in the nearshore environment.& &
Publisher: Elsevier BV
Date: 09-2020
Publisher: Copernicus GmbH
Date: 02-01-2020
Abstract: Abstract. Tropical cyclones have devastating impacts on the environment, economies, and societies, and may intensify in the coming decades due to climate change. Stable water isotopes serve as tracers of the hydrological cycle, as the fractionation process may leave distinct precipitation isotopic signatures. Here we present a record of daily precipitation isotope measurements from March 2014 to October 2015 for Metropolitan Manila, which is a first of a kind dataset for the Philippines and Southeast Asia, and analyze if there is an isotopic response to tropical cyclones. The most negative shift in δ18O value (−13.84 ‰) leading to a clear isotopic signal was caused by Typhoon Rammasun, which directly hit Metropolitan Manila. The average δ18O value of precipitation associated with tropical cyclones is −10.24 ‰, whereas the mean isotopic value for rainfall associated with non-cyclone events is −5.29 ‰. Further, the closer the storm track to the s ling site, the more negative the isotopic values, indicating that in-situ isotope measurements can provide a direct linkage between isotopes and typhoon activities in the Philippines.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-16785
Abstract: & & Studies on recent on the deposits of recent tsunami and tropical cyclone events have provided the research community with new insights on the utility of their deposits. In addition, they also provide for the evaluation of some criticisms and knowledge gaps for future studies. There remain no globally applicable sedimentological criteria for differentiating between tsunami and storms deposits in either washover sandsheets or boulder deposits. What has been compiled for the many deposits attributed to tsunamis and storms is a suite of geomorphological or sedimentary features or commonalities, often referred to as signatures. All deposits regardless of type must be considered in terms of the local setting, and be carefully analysed for spatial relationships. Geomorphological characteristics and sedimentary features must also be considered in the context of the local environment. When considered alone many of the reported signatures for storms and tsunamis are equivocal. In fact, many of the signatures from the literature for tsunami or storm deposition, including the presence of marine microfauna or increases in particular elemental concentrations merely indicate the marine source of the material. Hence, storm surges, sea level change or co-seismic subsidence may show similar sedimentological characteristics. Efforts to differentiating between tsunami and storm deposits have stagnated and new approaches are needed. Addressing this need I will discuss my views on where the coastal geohazard community can go from here.& &
Publisher: American Geophysical Union (AGU)
Date: 2019
DOI: 10.1029/2018JC014695
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-9341
Abstract: & & The 2004 Indian Ocean Tsunami tragically underscored the practical implication of understanding the Sumatran subduction zone and its tsunami potential. Further paleo-tsunami research is needed to fully inform the assessment of future tsunami hazards for coastal regions of the Indian Ocean. However, the Covid-19 pandemic has severely limited the ability of many international teams to conduct field investigations of paleo-tsunami sites in Southeast Asia. In collaboration between Syiah Kuala University in Indonesia and Nanyang Technological University in Singapore our team has been investigating the paleo-tsunami history of Sumatra for more than 10 years. This year, in order to facilitate training of junior staff at Syiah Kuala University we recorded a number of coring, s ling and sediment description videos combined with virtual workshops. Written material, as well as regular meetings via zoom, have made co-ordination of fieldwork possible. We also uploaded all data to cloud services immediately following fieldwork to allow everyone in the project to have access to it quickly. This data now consists of more than 500 photographs, field description files, and field reports.& & & & Previously our efforts have concentrated along the northern half of the Aceh province, which was devastated by the 2004 Indian Ocean Tsunami. Over the past 12 months, we have extended our field research ~250 km southwards along the western coastline of Sumatra. Despite the pandemic, we have been able to investigate 4 new coastal wetland sites and identify between 1 and 5 potential paleo-tsunami layers at each site at depths of 1.7 to 4.5 m. More than 50 s les of the sediments have been s led and are currently being analyzed to confirm their marine origin and the chronology of the events they represent.& &
Publisher: Springer Science and Business Media LLC
Date: 08-06-2023
DOI: 10.1038/S43247-023-00868-5
Abstract: Low elevation equatorial and tropical coastal regions are highly vulnerable to sea level rise. Here we provide probability perspectives of future sea level for Singapore using regional geological reconstructions and instrumental records since the last glacial maximum ~21.5 thousand years ago. We quantify magnitudes and rates of sea-level change showing deglacial sea level rose from ~121 m below present level and increased at averaged rates up to ~15 mm/yr, which reduced the paleogeographic landscape by ~2.3 million km 2 . Projections under a moderate emissions scenario show sea level rising 0.95 m at a rate of 7.3 mm/yr by 2150 which has only been exceeded (at least 99% probability) during rapid ice mass loss events ~14.5 and ~9 thousand years ago. Projections under a high emissions scenario incorporating low confidence ice-sheet processes, however, have no precedent during the last deglaciation.
Publisher: Elsevier BV
Date: 07-2010
Publisher: Copernicus GmbH
Date: 14-03-2022
Publisher: Copernicus GmbH
Date: 30-04-2019
Abstract: Abstract. Seismogenic tsunami hazard assessments are highly dependent on the reliability of earthquake source models. Here in a study of the Manila subduction zone (MSZ) system, we combine the geological characteristics of the subducting plate, the geometry, and coupling state of the subduction interface to propose a series of fault rupture scenarios. We ide the subduction zone into three rupture segments: 14° N–16° N, 16° N–19° N and 19° N–21.7° N inferred from geological structures associated with the down-going Sunda plate. Each of these segments is capable of generating earthquakes of magnitude between Mw 8.5+ and Mw 9+, assuming a-1000-year seismic return period as suggested by previous studies. The most poorly constrained segment of the MSZ lies between 19° N–21.7° N, and here we use both local geological structures and characteristics of other subduction zone earthquakes around the world, to investigate the potential rupture characteristics of this segment. We consider multiple rupture modes for tsunamigenic-earthquake type and megathrust-splay fault earthquakes. These rupture models facilitate an improved understanding of the potential tsunami hazard in the South China Sea (SCS). Hydrodynamic simulations demonstrate that coastlines surrounded the SCS could be devastated by tsunami waves up to 10-m if large megathrust earthquakes occur in these segments. The regions most prone to these hazards include west Luzon of Philippines, southern Taiwan, the southeastern China, central Vietnam and the Palawan Island.
Publisher: Elsevier BV
Date: 09-2019
Publisher: Wiley
Date: 26-01-2020
Publisher: Elsevier BV
Date: 11-2021
Publisher: Seismological Society of America (SSA)
Date: 09-11-2021
DOI: 10.1785/0120210154
Abstract: The frontal sections of subduction zones are the source of a poorly understood hazard: “tsunami earthquakes,” which generate larger-than-expected tsunamis given their seismic shaking. Slip on frontal thrusts is considered to be the cause of increased wave heights in these earthquakes, but the impact of this mechanism has thus far not been quantified. Here, we explore how frontal thrust slip can contribute to tsunami wave generation by modeling the resulting seafloor deformation using fault-bend folding theory. We then quantify wave heights in 2D and expected tsunami energies in 3D for both thrust splays (using fault-bend folding) and down-dip décollement ruptures (modeled as elastic). We present an analytical solution for the d ing effect of the water column and show that, because the narrow band of seafloor uplift produced by frontal thrust slip is d ed, initial tsunami heights and resulting energies are relatively low. Although the geometry of the thrust can modify seafloor deformation, water d ing reduces these differences tsunami energy is generally insensitive to thrust r parameters, such as fault dip, geological evolution, sedimentation, and erosion. Tsunami energy depends primarily on three features: décollement depth below the seafloor, water depth, and coseismic slip. Because frontal ruptures of subduction zones include slip on both the frontal thrust and the down-dip décollement, we compare their tsunami energies. We find that thrust r s generate significantly lower energies than the paired slip on the décollement. Using a case study of the 25 October 2010 Mw 7.8 Mentawai tsunami earthquake, we show that although slip on the décollement and frontal thrust together can generate the required tsunami energy, & % was contributed by the frontal thrust. Overall, our results demonstrate that the wider, lower litude uplift produced by décollement slip must play a dominant role in the tsunami generation process for tsunami earthquakes.
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-10428
Abstract: To date most natural hazard risk assessments in Australasia do not incorporate long-term and/or prehistoric records of extreme events and coastal development continues to rely on short historical records as a re& #64258 ection of the long-term behaviour of a hazard. In some locations such as southern China or the Philippines historical records may be appropriate as consistent records have been kept for several centuries or even a millennium. However, for much of the Asia-Pacific this is rare as the historical archives rarely stretch beyond World War II. Clearly such short records are inadequate for determining the natural variability of a hazard at multi-decadal timescales and for the extrapolation of extreme events. & While it is well known that the historical record is fragmentary, incomplete and limited in spatial balance, the historical record does provide a key link between instrumental datasets and the prehistoric record that allows for the detailed reconstruction of past events. Here, we compare known historical tropical cyclone events to recent ones in Western Australia (UC1921 and cyclone Herbie) and the central Philippines (Typhoon Haiyan and Ty1897) as ex les of integrated studies. The two ex les demonstrate the utility of the integrated approach and allow an examination of the similarities and differences between the events. Such efforts must become familiar to those outside of academia, as familiarity breeds awareness and it is through awareness and adoption that the true potential of integrating across disciplines will be recognized.
Publisher: Elsevier BV
Date: 2011
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-11157
Abstract: In the context of warming climate and rising sea level, records from the early-to-mid Holocene provide important analogues to investigate how the environment responds to such changes. The Sunda shelf provides favourable conditions to reconstruct past environmental change as the presence of numerous large paleo-valley systems and high sedimentation rates allow transgressive deposits from the early-mid Holocene sea-level rise to accumulate continuously in topographic depressions.& To this end, we analysed the sedimentological, geochemical and micropaleontological characteristics of a sediment core (GRBH03) to investigate early-to-mid Holocene environmental changes in southern Singapore. We constrained the chronology with ten radiocarbon dates that were placed in Bchron age-depth model. Using a multi-proxy approach (e.g., grain size distribution, loss on ignition and XRF core-scanning), supported by benthic foraminifera, three sedimentary units were identified in GRBH03. Sedimentary unit I was found at the base of the core. This unit was characterised by a dark grey sandy silt unit deposited from about 9.0 to 8.9 cal ka BP. Few or no foraminifera were found in this unit, likely due to degradation of organic material. Sedimentary unit II was a blue-grey marine mud that was deposited between 8.8 and 5.8 cal ka BP. Within the marine mud unit, foraminiferal assemblages show a transition to shallow marine environment from about 8.8 to 6.4 cal ka BP as open marine species (e.g., Murrayinella murrayi and Bulimina sp. cf. B. marginata) become more abundant up-core. Subsequently, brackish species such as Muyrrayinella globosa and Ammonia veneta started to dominate mud unit assemblages, reflecting a transition from shallow marine to brackish environments, likely associated with decelerating sea level rise. The marine unit is then overlain by the sedimentary unit III, which is a shelly-silt unit deposited after 5.9 cal ka BP. This unit was mostly barren of foraminifera, which may be attributed to a high-energy marginal marine environment where conditions were unfavourable for foraminiferal preservation. Our study show that changes in sedimentary units and foraminiferal assemblages present in GRBH03 are linked to varying rate of relative sea-level rise during the early-to-mid Holocene.&
Publisher: Elsevier BV
Date: 06-2007
Publisher: Copernicus GmbH
Date: 30-04-2019
Publisher: Springer Science and Business Media LLC
Date: 31-05-2023
DOI: 10.1038/S43247-023-00844-Z
Abstract: Shark Bay Marine Park is a UNESCO World Heritage Property located in a region of marginal tropical cyclone influence. Sustainable management of this unique environment as the climate changes requires a quantified understanding of its vulnerability to natural hazards. Here, we outline a structured analysis of novel historical archive information that has uncovered reports of an extreme storm surge associated with a Tropical Cyclone in 1921 that generated remarkable overland flow which left fish and sharks stranded up to 9.66 km (6 miles) inland. Weighted information from historical archives is placed in a new framework and provide inputs to modelling of this event which improves the understanding of its magnitude and furnishes records of the impacts of what occurred on that day and notably also in the years following. The suite of plausible tracks that reproduce the historical data contextualise the storm as a marginal Category 4 or 5 storm and its return interval as equivalent or slightly greater than the current local planning level for coastal flooding in the region. The outcome underscores the global importance of examining the probable maximum event for risk management in areas of marginal cyclone influence where vulnerable ecosystems or vital regional infrastructure of key economic importance are located, and the need to factor in TC risk in marine conservation and planning in the Shark Bay World Heritage Property.
Publisher: Wiley
Date: 27-05-2011
Publisher: American Geophysical Union (AGU)
Date: 11-02-2022
DOI: 10.1029/2021GL095710
Abstract: The small number of reliable long‐term (i.e., yrs) tide gauges in tropical locations is a major source of uncertainty in modern sea‐level change. Coral microatolls record relative sea‐level (RSL) change over their lifetimes and have the potential to extend the instrumental record. Here, we examined a 20th and 21st century RSL record from two living coral microatolls from Mapur Island, Indonesia, which produced 16 sea‐level index points. We validated and combined the living coral microatoll data with tide gauge data to show RSL at Mapur Island was 0.0 ± 1.6 mm/yr (2σ) from 1915 to 1990 and 1.0 ± 2.1 mm/yr (2σ) from 1990 to 2019. Through the addition of microatoll RSL data we extended the record of modern sea‐level change by over 50 years and reduced its uncertainty by ∼50%.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-13902
Abstract: & & The Maritime Continent (MC) is located within the Indo-Pacific Warm Pool, which is known as the largest area of warm sea surface temperatures with the highest rainfall on Earth that drives the global atmospheric and hydrologic circulation. The complex climatic system of the MC is controlled by large-scale phenomena such as the seasonal migration of the Intertropical Convergence Zone which causes the northwest and southeast monsoon circulation in the region as well as tropical Indo-Pacific climate phenomena, the Indian Ocean Dipole in the west and the El Ni& #241 o-Southern Oscillation operating to the east of the MC. In addition to interactions of these climate phenomena, their influence varies across the region due to island topography and ocean& #8211 atmosphere fluxes. Despite dedicated efforts, a comprehensive picture of the impacts of abrupt climate events such as the & #8216 .2 ka event& #8217 during the Holocene on the MC has proved elusive. Here we use sedimentology and stable isotopes of benthic foraminifera collected from the marginal marine sediments off the Kallang River Basin, Singapore to reconstruct paleoenvironmental history of the early-mid Holocene. Owing to the high sedimentation rate (~4.4 mm/yr), the timing and nature of the & #8216 .2 ka event& #8217 was examined in detail in this region making this an invaluable and unique archive to study up to sub-centennial changes. Comparison of the Kallang record with other high-resolution marine and absolutely dated terrestrial archives speleothems revealed that the timing of the onset of & #8216 .2 ka event& #8217 in the western IPWP region lags the cooling in the North Atlantic and that of Asian and Indian monsoon failure, by ~100years possibly implying a north-south signal propagation. The termination of the & #8216 .2 ka event& #8217 , however may have occurred near synchronously between high and low tropical regions at ~7.96ka BP possibly linked via both atmospheric and oceanic processes.& & & & & & &
Publisher: Elsevier BV
Date: 10-2012
Publisher: Research Square Platform LLC
Date: 12-05-2022
DOI: 10.21203/RS.3.RS-1611443/V1
Abstract: The most prominent abrupt climate event during the Holocene, the ‘8.2 ka event’, was characterized by severe cooling at high northern latitudes causing erse hydroclimate shifts globally. To date, a precise understanding of the hydroclimate response of the Indo-Pacific Warm Pool (IPWP) region to abrupt climate changes in the North Atlantic around 8.2 ka remains elusive. Here we present a high-resolution stable carbon isotope record on foraminifera species Asterorotalia pulchella and sediment characteristics of a marine sediment core from the Kallang River Basin, Singapore. Foraminifer stable isotope data in concert with sedimentological proxies provide coherent evidence of weakened rainfall for ~ 180 years in the western tropical Indo-Pacific region from ~ 8.14 ka to 7.96 ka BP. A robust age model suggests that the timing of the onset of reduced convective activity in the western IPWP region lags the cooling in the North Atlantic and the synchronous droughts in the Asian and Indian monsoon regions, by ~ 100years possibly implying a north-south signal propagation via oceanic route that operates on centennial scales. The termination of the ‘8.2 ka event’, however may have occurred near synchronously between high and low tropical regions at ~ 7.96ka BP possibly linked via both atmospheric and oceanic processes.
Publisher: Coastal Education and Research Foundation
Date: 2008
DOI: 10.2112/05-0487.1
Publisher: Wiley
Date: 07-03-2022
DOI: 10.1002/ESP.5292
Abstract: River deltas are strongly affected by demographic growth and by the intensification of land use. The migration of deltaic coastlines is often rapid, threatening urban settlements, coastal farming, and coastal biotopes. Some deltas benefit from centuries of monitoring, such that the evolution of their coastline is well documented. For most deltas, however, such long records do not exist. The study of their geomorphological evolution can benefit from overlapping maps drafted over time, combined with aerial photographs and satellite images, to track the evolution of fluvial and coastal landforms. Both fluvial and coastal landforms are sensitive to variations in water and sediment supply, such that covariations in the evolution of these landforms, or the lack thereof, provide clues on the contribution of water and sediment supply to delta evolution. We document the evolution of river channels and coastlines in the delta of the Aceh River in northwest Sumatra, by overlying maps, ortho‐rectified aerial photographs, and satellite images covering the past 130 years. We assess the accuracy of the overlays, and then use multivariate statistics to analyze the co‐evolution of fluvial and coastal landforms. We propose that a progressive decrease in sediment supply spurred river channel lengthening and narrowing, landward migration of the shoreline, and narrowing of beach ridges. The 2004 Indian Ocean tsunami generated an instantaneous retreat of the coastline that amounts to ∼53% of the coastal retreat from 1884 to 2019 ce . Post‐tsunami evolution is marked by an irreversible acceleration of previous trends. Beach ridges located up‐drift of rivers and tidal channel mouths are more sensitive to long‐term landward retreat and tsunamigenic erosion.
Publisher: Elsevier BV
Date: 10-2012
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-1600
Abstract: & & Ludao Island in south eastern Taiwan regularly experiences strong Pacific typhoons.& Fieldwork was undertaken to investigate the characteristics of a boulder field comprising massive limestone and volcanic clasts (10& sup& & /sup& & #8211 & sup& & /sup& kg) on the exposed SE coast. & Old large clasts on the Holocene emerged platform provide evidence for multiple high-energy palaeowave events. & Of particular interest were clasts stacked and imbricated together to form distinct boulder trains. & Inferred minimum flow velocities of 4.3& #8211 .8 m/s were needed for their deposition. & What can imbricated boulder trains tell us about the wave processes and geomorphic influences responsible? & One hypothesis here is that localized funnelling of water flow through narrow relict channels is able to concentrate onshore flow energy into powerful jets. & These channels represent inherited (fossil) spur-and-groove morphology, oriented perpendicular to the modern reef edge, now overdeepened by subaerial karstic solution. & Support for this idea is the location and train-of-direction of the main imbricated boulder cluster at the landward head of one such feature. & Geomorphic controls lifying wave-breaking flow velocities across Ludao's coastal platform mean that a palaeotyphoon origin is sufficient to account for large rock clast stacking and imbrication, without recourse to a tsunami hypothesis.& &
Publisher: Inter-Research Science Center
Date: 28-03-2011
DOI: 10.3354/MEPS09019
Publisher: Copernicus GmbH
Date: 18-05-2022
DOI: 10.5194/NHESS-22-1665-2022
Abstract: Abstract. The tsunami hazard posed by the Flores back-arc thrust, which runs along the northern coast of the islands of Bali and Lombok, Indonesia, is poorly studied compared to the Sunda Megathrust, situated ∼250 km to the south of the islands. However, the 2018 Lombok earthquake sequence demonstrated the seismic potential of the western Flores Thrust when a fault r beneath the island of Lombok ruptured in two Mw 6.9 earthquakes. Although the uplift in these events mostly occurred below land, the sequence still generated local tsunamis along the northern coast of Lombok. Historical records show that the Flores fault system in the Lombok and Bali region has generated at least six ≥Ms 6.5 tsunamigenic earthquakes since 1800 CE. Hence, it is important to assess the possible tsunami hazard represented by this fault system. Here, we focus on the submarine fault segment located between the islands of Lombok and Bali (below the Lombok Strait). We assess modeled tsunami patterns generated by fault slip in six earthquake scenarios (slip of 1–5 m, representing Mw 7.2–7.9+) using deterministic modeling, with a focus on impacts on the capital cities of Mataram, Lombok, and Denpasar, Bali, which lie on the coasts facing the strait. We use a geologically constrained earthquake model informed by the Lombok earthquake sequence, together with a high-resolution bathymetry dataset developed by combining direct measurements from the General Bathymetric Chart of the Oceans (GEBCO) with sounding measurements from the official nautical charts for Indonesia. Our results show that fault rupture in this region could trigger a tsunami reaching Mataram in min and Denpasar in ∼ 23–27 min, with multiple waves. For an earthquake with 3–5 m of coseismic slip, Mataram and Denpasar experience maximum wave heights of ∼ 1.6–2.7 and ∼ 0.6–1.4 m, respectively. Furthermore, our earthquake models indicate that both cities would experience coseismic subsidence of 20–40 cm, exacerbating their exposure to both the tsunami and other coastal hazards. Overall, Mataram is more exposed than Denpasar to high tsunami waves arriving quickly from the fault source. To understand how a tsunami would affect Mataram, we model the associated inundation using the 5 m slip model and show that Mataram is inundated ∼ 55–140 m inland along the northern coast and ∼230 m along the southern coast, with maximum flow depths of ∼ 2–3 m. Our study highlights that the early tsunami arrival in Mataram, Lombok, gives little time for residents to evacuate. Raising their awareness about the potential for locally generated tsunamis and the need for evacuation plans is important to help them respond immediately after experiencing strong ground shaking.
Publisher: Elsevier BV
Date: 11-2015
Publisher: American Geophysical Union (AGU)
Date: 12-2022
DOI: 10.1029/2021EF002607
Abstract: Asia has the fastest growing population and economy, but it is also the most disaster‐prone region in the world. Resilience to disaster impacts from natural hazards will be key to the long‐term sustainability of this rapidly growing region. The first step to building resilience is to identify the key threats that this region faces. We describe these key threats as Black Elephants: a cross between a “black swan” and the proverbial "elephant in the room" — they are extreme events that are known but difficult to address and often ignored. We examine the primary drivers of these looming risks and find that the drivers include underestimated or intensifying hazards, growing exposure, high vulnerability, and unaccounted complexities from multi‐hazard events. In mitigating these key risks, we discuss psychological barriers to action and highlight the importance of information, language, and hope. The known but complex impacts from natural hazards in Asia must be further acknowledged and managed in order to build a more sustainable, resilient future in an increasingly globally connected world.
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-10851
Abstract: Both retrospective tsunami analyses and assessments of future tsunami hazards depend on accurate modeling of how tsunami waves generated offshore propagate through shallow waters near the coast. Accurate models of tsunami propagation in shallow water require high-resolution bathymetric maps, but these are often inaccessible because of the time and cost required to acquire them. In addition, tsunami models based on high resolution bathymetry have high computational processing requirements. Hence, it has been common to use globally available datasets with coarser resolutions, such as the GEBCO dataset, in modeling.Here, we examine how variations in bathymetric resolution, from 5 m to & #8764 m (GEBCO), affect simulated coastal tsunamis. Our case study includes four study sites with available LiDAR bathymetry datasets (1 m resolution). At each site 30 sets of points were randomly extracted from the LiDAR bathymetry datasets and used to generate bathymetric grids with resolutions of 5, 10, 20, 30, 40, 50, 100, 200, and 300 m at each site. These were also compared to a bathymetry based purely on the GEBCO dataset for that region (& #8764 m resolution), that we modified to match the coastlines of the other bathymetry models. Tsunami waves offshore were generated by setting up an instantaneous rupture sourced from a hypothetical fault model and we used the commonly used COMCOT software to model tsunami propagation towards the coast.Using the model run with 5 m resolution bathymetry as a high resolution reference model, we observed that bathymetric grids with resolutions of 10 & #8211 50 m can reproduce coastal wave heights reasonably well, with the maximum wave height overestimated by & #8804 % or underestimated by & #8804 %. For coarser bathymetric grids, however (& #8805 m resolution), there is an increasing trend of underestimation. Wave heights are underestimated by at least 10% and with up to 30%, 40% and 60% underestimation for bathymetric resolutions of 100, 200, and 300 m, respectively. Notably, the commonly used GEBCO model underestimated coastal tsunami heights by as much as 70%. We also examined the impact on tsunami arrival time: and found that resolutions of 10 & #8211 50 m exhibited a first wave arriving & #8764 % earlier than expected, while coarser resolutions showed more variability, with the first wave arriving either & #8804 % later or & #8804 % earlier. For GEBCO-based models, the& arrival time estimate tends to be underestimated by 10 & #8211 30% or overestimated by 20 & #8211 50%. Our study demonstrates that using GEBCO bathymetry in numerical modeling of tsunami wave propagation in the coastal region likely leads to a significant underestimation of the wave height, with the wave also predicted to arrive too early. However, a reasonably accurate result can be achieved using a bathymetric resolution in the 10 m & #8211 50 m range, and is achievable with reasonable computational efficiency. This study highlights the importance of shallow bathymetry in the numerical modeling of tsunami propagation.
Publisher: Springer Science and Business Media LLC
Date: 27-09-2019
Publisher: Elsevier BV
Date: 2011
Start Date: 05-2016
End Date: 12-2022
Amount: $374,516.00
Funder: Australian Research Council
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